Research into the addition of allyl organometallics to carbonyl compounds and their derivatives continues to proceed unabated—a consequence of the fact that the resulting homoallylic products have proven to be valuable synthons [S. E. Denmark and N. G. Almstead, Modern Carbonyl Chemistry, ed. J. Otera, Wiley-VCH, Weinheim, 2000, ch. 10; Y. Yamamoto and N. Asao, Chem. Rev., 1993, 93, 2207; and W. R. Roush, Comprehensive Organic Synthesis, ed. B. M. Trost, I. Fleming and C. H. Heathcock, Pergamon, Oxford, 2nd edn., 1991, vol. 2, pp 1-53]. The majority of the research, however, has focused on the addition of these organometallics to aldehydes. For example, the reaction of
has previously been described by Kobayashi et al. [M. Sugiura, K. Hirano and S. Kobayashi, J. Am. Chem. Soc., 2004, 126, 7182; S. Kobayashi, K. Hirano, M. Sugiura, Chem. Commun., 2005, 104].
Although to a lesser extent, there have been some recent examples of allylation of ketones [L. F. Tietze, K. Schiemann, C. Wegner and C. Wulff, Chem. Eur. J., 1998, 4, 1862; S. Casolari, D. D'Addario and E. Tagliavini, Org. Lett., 1999, 1, 1061; R. Hamasaki, Y. Chounan, H. Horino and Y. Yamamoto, Tetrahedron Lett., 2000, 41, 9883; R. M. Kamble and V. K. Singh, Tetrahedron Lett., 2001, 42, 7525; J. G. Kim, K. M. Waltz, I. F. Garcia, D. Kwiatkowski and P. J. Walsh, J. Am. Chem. Soc., 2004, 126, 12580; T. R. Wu, L. Shen and J. M. Chong, Org. Lett., 2004, 6, 2701; and Y.-C. Teo, J.-D. Goh and T.-P. Loh, Org. Lett., 2005, 7, 2743]. Until recently, the expansion of the substrate scope to include imines and their derivatives had received limited attention. Some recent examples of the addition of allylorganometallics to aldimine derivatives can be found in the following references [C. Bellucci, P. G. Cozzi and A. Umani-Ronchi, Tetrahedron Lett., 1995, 36, 7289; H. Nakamura, K. Nakamura and Y. Yamamoto, J. Am. Chem. Soc., 1998, 120, 4242; F. Fang, M. Johannsen, S. Yao, N. Gathergood, R. G. Hazell and K. A. Jørgensen, J. Org. Chem., 1999, 64, 4844; T. Gastner, H. Ishitani, R. Akiyama and S. Kobayashi, Angew. Chem., Int. Ed., 2001, 40, 1896; H. C. Aspinall, J. S. Bissett, N. Greeves and D. Levin, Tetrahedron Lett., 2002, 43, 323; M. Sugiura, F. Robvieux and S. Kobayashi, Synlett, 2003, 1749; R. A. Fernandes and Y. Yamamoto, J. Org. Chem., 2004, 69, 735; S.-W. Li and R. A. Batey, Chem. Commun., 2004, 1382; I. Shibata, K. Nose, K. Sakamoto, M. Yasuda and A. Baba, J. Org. Chem., 2004, 69, 2185; and C. Ogawa, M. Sugiura and S. Kobayashi, Angew Chem., Int. Ed., 2004, 43, 6491]. As for the addition of allylorganometallics to ketimine derivatives, some recent examples have also been reported [C. Ogawa, M. Sugiura and S. Kobayashi, J. Org. Chem., 2002, 67, 5359; S. Yamasaki, K. Fujii, R. Wada, M. Kanai and M. Shibasaki, J. Am. Chem. Soc., 2002, 124, 6536; R. Berger, K. Duff and J. L. Leighton, J. Am. Chem. Soc., 2004, 126, 5686; H. Ding and G. K. Friestad, Synthesis, 2004, 2216].
However, there is yet no known synthetic methodology for the preparation of tertiary carbinamine compounds through diastereoselective allylation and crotylation of N-unsubstituted ketimines. New methodologies to solve the difficulties associated with making these valuable tertiary carbinamine compounds will no doubt have a tremendous impact in organic synthesis and in the chemical industry. New methodologies may also provide a new class of tertiary carbinamine compounds that cannot be obtained using conventional protocols. For example, the recent report of aminoallylation of aldehydes by Kobayshi and coworkers has already had a tremendous impact in organic synthesis [M. Sugiura, K. Hirano and S. Kobayashi, J. Am. Chem. Soc., 2004, 126, 7182; S. Kobayashi, K. Hirano, M. Sugiura, Chem. Commun., 2005, 104].